The sun doesn’t always shine on Earth, but in space, it shines all the time. That’s why some scientists say that, instead of putting solar panels on the ground—where passing clouds, the day-and-night cycle, and the Earth’s latitude all affect the strength of the sun’s rays—we should launch them into orbit and beam the energy back down to Earth. Solar panels in space aren’t as improbable as they sound: Solaren Corp., a California company, plans to deliver the first-ever electricity from space starting in 2016.

The idea for space-based solar power has been around since 1968, when Peter Glaser, a solar energy pioneer, first proposed it. According to Space Canada, a non-profit group that formed in 2008 to promote space-based solar power, solar panels in orbit around Earth could absorb 10 times as much energy as the ones on the ground. The sun’s rays would be converted into a focused microwave or laser beam, and zapped down to receiving stations here. In Canada, we only get so much sunlight to use as solar power, says George Dietrich, president of Space Canada; other energy sources, like nuclear power or hydrocarbons, “have long-term difficulties.” With concerns about global warming—and our growing demand for energy—space-based solar power is an increasingly attractive option, and Space Canada insists it could more than meet our needs.

But many hurdles remain, including what technology historian Jonathan Coopersmith calls “the giggle factor” of launching solar factories into space. Convincing the public that beaming a microwave at Earth is safe—the “Death Star factor,” he says—could be a challenge, too. But John C. Mankins, a former NASA executive and expert in space-based solar power, says the technology exists. In 2008, he led a team that captured solar energy from a Maui mountaintop and zapped it almost 150 km to Hawaii’s main island, proof it could be done. (Data travels to Earth from communications and direct broadcast television satellites in a similar fashion, Mankins notes.) “We don’t want the beam to be too intense, for safety reasons,” he says, adding that it would be “a fraction of the intensity of noontime sunlight.”

According to Cal Boerman, vice-president of electricity sales and delivery at Solaren, the beam—which is about two miles wide—would have a heating effect on humans or animals, like being out on a hot sunny day, minus the sunburn. “Airplanes can fly through it. Birds will be able to transit it,” he says. “It’s not like a death ray.” (The beam will travel down to a fenced-in receiving station, where it will be converted to electricity; workers carrying out tasks inside the beam would be shielded from it, Boerman says.)

But the biggest challenge, says Coopersmith, a professor at Texas A&M University, is cost. Today, space launches cost roughly $20,000 per kilogram, he says. To send up a solar-power satellite, which might weigh 3,000 tonnes, could cost $60 billion. But Solaren says its design is lightweight enough to work. The company recently signed a contract to sell California utility Pacific Gas & Electric 1,700 gigawatt hours per year, for 15 years, from a space-based solar array. That’s enough to power “thousands of homes,” Boerman says. As far as the cost, “our first plant will take four launches of the biggest rockets in the world,” he says. “It’s not lightweight by any means. But it’s affordable.”

Others are working toward it, too. Japan, a country with few energy resources of its own, announced plans to install a one gigawatt system—roughly equivalent of a medium-sized nuclear power plant—in geostationary orbit by the year 2030, and has already hired companies and researchers to make it happen. In the wake of the Louisiana oil spill, astronaut Buzz Aldrin was also talking it up. “The timing of the oil catastrophe,” he recently said, “is a great opportunity for re-evaluating solar energy from space.”

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About this author

Kate Lunau is a health and science writer at Maclean's Magazine, who previously reported for the Montreal Gazette. She's the recipient of several journalism awards, including the 2014 Yves Fortier Earth Science Journalism Award, and has been nominated for two National Magazine Awards. Like Elon Musk, she hopes to retire on Mars.

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Catching some rays

It makes sense in a lot of ways, but I'm puzzled about a few things.

(a) the delivery wavelength. Microwave frequencies are absorbed by moisture; they'll lose a lot of energy on the way through the atmosphere. With cloud cover it would be even worse. Visible wavelengths are easily scattered by clouds just as sunlight is, so it amounts to the same problem. Higher frequencies become dangerous. Lower frequencies (IR) might work if they're chosen very carefully to avoid absorption peaks in the atmosphere.

(b) If a location with little cloud cover is picked then visible wavelengths would work well (particularly at the low end of the wavelength range to avoid Rayleigh scattering), but in that case why not just use a reflector rather than converting to electrical with solar panels and then reconverting to optical with a laser? The efficiency and the mean time to failure are a lot higher with a mirror, and maintenance costs add up pretty quickly when you're dealing with something out in space.

(c) If it's geosynchronous, I think there are going to be problems capturing solar radiation 24 hours a day. If it's not geosynchronous, I think there are going to be problems delivering power to one geographical location 24 hours a day. Are they planning multiple receiver stations or a power storage unit (e.g. a capacitor) on board the satellite? I guess the third option is to use two or three satellites, one for the main power generation and the others as reflectors to bring the beam into target. That multiplies the cost of the system, though.

a) other sources say RF not microwaves… They would presumably look for a point at which both absorption in the atmosphere and in tissue is very small.

b) To make the system make economic sense, there would be a massive space mirror to focus the sunlight. The idea is that a massive mirror in space does not have to support its weight and so can be much less costly. (still expensive to get it there) It would focus the light onto a very expensive (but fairly small) array of space grade solar cells. These can be up to 40 % at converting concentrated sunlight to electicity. The claim is that they can convert this electicity in space to RF energy, beam it down and reconvert it at nearly 90% efficiency. That 90% is very important since it allows their beam not to be a "death ray" while still getting useful amounts of power. (I would guess that they would still want to push the power of the beam quite a bit higher for economic reasons)

c) a geosynchronous orbit has an altitude of about 36,000 km, with the Earth's radius being about 6,000 km. My quick estimate is that you are correct, but the shielding will only last about 10 minutes a day.

(1) Perhaps, but at RF the photon energy is considerably lower. This will make it more difficult to deliver power efficiently.

(2) Even if that's true (90% efficiency for the combined laser, transmission, and receiver? I'll believe that when I see it), wouldn't it be simpler to just use the mirror to beam the sunlight directly down to the receiver? Why go through a complex and inefficient solar array step in space? If the argument is that this allows for less lossy transmission because of the carrier frequency then I question whether the transmission savings outweigh the conversion losses, not to mention the added maintenance issues.

(3) I think it works out to about 75 minutes, actually, but anyway I think you're right: not a big loss.

Certainly agree with the above points. See more troubles:
– Practically solving the unavoidable problems described in (c) the system will have to switch from one receiver to another, thus if synchronization goes wrong we are going to have a system shooting the highly dangerous ray on the territories between the receivers. I do not even want to think about the situation if the control of this system is seized by terrorists or the military.
– The amount of energy needed to deliver all the system onto the orbit is tremendous. It will never be economical.
– I do not see much sense in the idea altogether – to support all energy needs of the existing population of the whole planet for the whole year it is enough to utilize sun energy that reaches the surface of our planet in less than 1 hour. Why again do we need to go into space to harvest energy?!

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